[PATCH net v2] net: ftgmac100: Disable hardware checksum on AST2600

[Joel Stanley]

On Fri, 13 May 2022 at 01:46, Dylan Hung <dylan_hung at aspeedtech.com> wrote:
>
> > -----Original Message-----
> > From: joel.stan at gmail.com [mailto:joel.stan at gmail.com] On Behalf Of Joel
> > Stanley
> > Sent: Friday, May 13, 2022 7:20 AM
> > To: David S . Miller <davem at davemloft.net>; Jakub Kicinski
> > <kuba at kernel.org>; Paolo Abeni <pabeni at redhat.com>; Benjamin
> > Herrenschmidt <benh at kernel.crashing.org>; Dylan Hung
> > <dylan_hung at aspeedtech.com>; David Wilder <dwilder at us.ibm.com>
> > Cc: openbmc at lists.ozlabs.org; netdev at vger.kernel.org;
> > linux-kernel at vger.kernel.org; David Wilder <wilder at us.ibm.com>
> > Subject: [PATCH net v2] net: ftgmac100: Disable hardware checksum on
> > AST2600
> >
> > The AST2600 when using the i210 NIC over NC-SI has been observed to
> > produce incorrect checksum results with specific MTU values. This was first
> > observed when sending data across a long distance set of networks.
> >
> > On a local network, the following test was performed using a 1MB file of
> > random data.
> >
> > On the receiver run this script:
> >
> >  #!/bin/bash
> >  while [ 1 ]; do
> >         # Zero the stats
> >         nstat -r  > /dev/null
> >         nc -l 9899 > test-file
> >         # Check for checksum errors
> >         TcpInCsumErrors=$(nstat | grep TcpInCsumErrors)
> >         if [ -z "$TcpInCsumErrors" ]; then
> >                 echo No TcpInCsumErrors
> >         else
> >                 echo TcpInCsumErrors = $TcpInCsumErrors
> >         fi
> >  done
> >
> > On an AST2600 system:
> >
> >  # nc <IP of  receiver host> 9899 < test-file
> >
> > The test was repeated with various MTU values:
> >
> >  # ip link set mtu 1410 dev eth0
> >
> > The observed results:
> >
> >  1500 - good
> >  1434 - bad
> >  1400 - good
> >  1410 - bad
> >  1420 - good
> >
> > The test was repeated after disabling tx checksumming:
> >
> >  # ethtool -K eth0 tx-checksumming off
> >
> > And all MTU values tested resulted in transfers without error.
> >
> > An issue with the driver cannot be ruled out, however there has been no bug
> > discovered so far.
> >
> > David has done the work to take the original bug report of slow data transfer
> > between long distance connections and triaged it down to this test case.
> >
> > The vendor suspects this this is a hardware issue when using NC-SI. The fixes
> > line refers to the patch that introduced AST2600 support.
> >
> > Fixes: 39bfab8844a0 ("net: ftgmac100: Add support for DT phy-handle
> > property")
> > Reported-by: David Wilder <wilder at us.ibm.com>
> > Signed-off-by: Joel Stanley <joel at jms.id.au>

> Reviewed-by: Dylan Hung <dylan_hung at aspeedtech.com>

Thank you Dylan. I've added your r-b to v3, as the only changes are to
the wrapping of the commit message.